(1) Field of the Invention
This invention is in the field of radiation dosimeters of the type which are capable of accurately measuring ionizing radiation doses of large magnitudes.
(2) Description of the Prior Art
A variety of ionizing radiation dosimeters are known by those skilled in the art. Conventionally, these are of the type which must be removed from the area of radiation to obtain a measurement of the dose, exemplified by thermoluminescence or ceric sulphate dosimeters. When the radiation doses are being administered in vacuum chambers or other inaccessible locations, and repeated radiation dose measurements are needed from the test point, the disruption associated with the use of a dosimeter requiring removal for measurement becomes a significant hindrance.
Semiconductor type devices have been used as direct reading radiation dose measuring sensors, but generally exhibit either marginal accuracy or permanent radiation effects. Metal oxide semiconductor field effect transistors (MOSFETs) and metal oxide semiconductor capacitors (MOSCs) are representative. The accuracy of these semiconductors is usually limited to .+-.5% when the devices are selected from the same semiconductor wafer and .+-.20% when this selective process is not exercised. Furthermore, devices such as MOSFETs exhibit radiation effects, in the form of permanent saturation, at doses in the range of 40 K rads (Si). Such devices become completely inadequate when the dose levels to which they are to be subjected are two orders of magnitude larger.